Engine runaway preventing safety means associated with a distributor-type fuel injection pump

ABSTRACT

In a fuel injection pump, particularly of the distributor type wherein the fuel metering is effected electronically as a function of engine parameters, the pump work chamber can be depressurized (and thus fuel injection interrupted) through a bypass port which is opened by a centrifugal shuttle when the engine rpm exceeds a predetermined safe maximum value.

United States Patent Eheim 1 Oct. 15, 1974 [5 ENGINE RUNAWAY PREVENTING SAFETY 2,775,233 [2/1956 Bischoff 123/139 AF MEANS ASSOCIATED WITH A 2,828,727 4/1958 Fischer 123/139 BC 2,937,628 5/1960 Mayr 123/198 DB DISTRIBUTOR-TYPE FUEL INJECTION 3,119,381 1/1964 Cummins 123/139 AF PUMP 3,161,133 12/1964 Hutcheon 123/139 BC 75 Inventor: Franz Eheim, Stuttgart, Germany 3,661,130 5/1972 Eheim 123/140 A 3,680,537 8/1972 Suda 123/139 E [73] Assignee: Robert Bosch GmbH, Stuttgart, 3,724,436 4/1973 Nagata ct a1... 123/139 E Germany [22] Filed: Aug. 4, 1972 Primary Examiner-Laurence M. Goodridge Assistant ExaminerC0rt Flint 1 App! 277862 Attorney, Agent, or FirmEdwin E. Greigg [30] Foreign Application Priority Data Aug. 4, 1971 Germany 2138994 [57] ABSTRACT In a fuel injection pump, particularly of the distributor [52] 123/140 123/140 0 2; type wherein the fuel metering is effected electroni- [511 Int Cl F02! 5/00 cally as a function of engine parameters, the pump [58] Field 139 AF work chamber can be depressurized (and thus fuel in- 03/140 140 B DB 140 jection interrupted) through a bypass port which is opened by a centrifugal shuttle when the engine rpm [56] References Cited exceeds a predetermined safe maximum value.

2,003,478 6/1935 Bovard 123/139 AF ENGINE RUNAWAY PREVENTING SAFETY MEANS ASSOCIATED WITH A DISTRIBUTOR-TYPE FUEL INJECTION PUMP BACKGROUND OF THE INVENTION This invention relates to a fuel injection pump, particularly of the distributor type, wherein the fuel quantities to be delivered to the engine are metered electrically by a rotary magnetic system. In a distributor-type fuel injection pump of the aforenoted type (such as disclosed in German Published Application DOS l,9l0,l l2 which corresponds to U.S. Pat. No. 3,630,643), the metering of the delivered fuel quantities is effected by a rotary magnetic system as a function of engine parameters. It is a disadvantage of this type of fuel quantity control that in case of a malfunctioning of one of the electronic components, the delivered fuel quantities may increase, causing a possible runaway of the internal combustion engine with which the fuel injection pump is associated.

It is an object of the invention to provide a distributor-type fuel injection pump which is free from the aforenoted disadvantage.

Briefly stated, according to the invention, there is provided an rpm-responsive centrifugal component and a bypass channel associated therewith. When a predetermined rpm is exceeded, the centrifugal component opens the bypass channel and, as a result, the pump work chamber is automatically depressurized.

The invention will be better understood as well as further objects and advantages will become more apparent from the ensuing detailed specification of a preferred, although exemplary embodiment taken in conjunction with the drawing wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a longitudinal sectional view of the entire distributor-type fuel injection pump and FIG. 2 is a sectional view along line Il--II of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to FIG. 1, there is shown a magnet l which is rotatably held between two coils 2 (only one visible). The two coils 2 are mounted on a core 3 in such a manner that a closed magnetic circuit may be formed through the rotary magnet l and the core 3. The rotary magnet is fixedly attached to a shaft 4 which is journaled in a support block 5 and which carries, at its mid portion, a cam disc 6 which, in turn, actuates, for example, an inductive transducer 8 through a follower 7. All electric conductors associated with the components 2 and 8 are accessible from the outside through prongs 48 connected to said components by a plate 46 and contact springs 45.

The transmission of the rotary motion of the shaft 4 to a control throttle 10 is effected by means of a crank 11 which is rigidly secured to the shaft 4 and by means of a pin 12 which extends into a slot 13 of the control throttle 10. Between the shaft 4 and the control throttle 10 there is arranged an axially extending spring 14 which urges the control throttle with its pointed terminus 15 against the base 16 of a bore 17.

The fuel is forced by a feed pump through a channel 20 into an annular chamber 21 and therefrom through a bore 22 which is in communication with the bore 17. The flow passage section of the bore 22 is varied as a function of the position of the control throttle 10. This control is effected by a control groove 23 which is provided on the control throttle l0 and which overlaps the mouth of the bore 22 to a greater or lesser extent. From the bore 17 the fuel is admitted to a port 24 which, dependent upon the position of the distributor shaft 25 driven by a pump drive shaft 44, communicates with selected intake bores 26. The latter merge into a longitudinal bore 27 which at one end communicates with a pump work chamber 28 accommodating two reciprocating pistons 30. Upon rotation of the distributor shaft 25, the pistons 30 are pressed inwardly by means of cams which are provided on the inner face of a ring 31. Between the pistons 30 and the ring 31 there are provided two guided rollers 32. From the pump work chamber 28 the fuel is delivered during the pressure stroke of the pistons 30 through the longitudinal bore 27 into a distributor bore 33 which, as the distributor shaft 25 rotates, sequentially communicates with a plurality of channels 34 each associated with a separate fuel injection valve, not shown.

From the pump work chamber 28 there extends axially a bore 37 which, in a determined position of a centrifugal shuttle 38, communicates with a bore 39 serving as a discharge or bypass channel. When the centrifugal shuttle 38 assumes its aforenoted position, the pressurized fuel from the pump work chamber is discharged into the pump housing 40 and therefrom the fuel mayflow back into the fuel tank through a return port 41.

Turning. now to FIG. 2, the centrifugal shuttle 38 comprises a centrifugal weight 50 and a piston plunger 51 affixed thereto. The piston plunger 51 is slidable in a bore 52 provided in the shaft 25 and extending normal to the axis thereof. The plunger 51 is provided with an annular groove 53 which in any position of the piston plunger is in continuous communication with the bore 37 (not shown in FIG. 2). The displacement of the centrifugal shuttle 38 as a result of the centrifugal forces generated upon the rotation of the distributor shaft 25, is opposed by the force of a spring 54, the bias of which is changeable by means of nuts 55. The spring at one end engages a spring seat disc 56 and at its other end is in contact with an abutment sleeve 57.

The delivered fuel quantities are controlled at the suction side of the distributor-type fuel injection pump by means of the control throttle 10, the position of which is determined by means of the rotary magnetic system 1, 2, 3 as a function of engine parameters (such as temperature and rpm of the internal combustion engine). The position of the control throttle 10 is continuously supervised by the inductive transducer 8. In order to prevent the rpm of the engine from exceeding a maximum permissible value which would occur for example, as a result of an excessive fuel quantity metered at the control throttle 10, due to a malfunction of the electronic apparatus controlling the rotary magnetic system, the centrifugal shuttle 38, beyond a predetermined rpm of the shaft 25, connects the pump work chamber 28 with the inside of the pump housing 40 through the bores 37, 39. Consequently, the pump work chamber 28 is depressurized and the fuel injection through the fuel injection valves is interrupted. The path of motion of the centrifugal shuttle 38 is limited by the abutment sleeve 57. Thus, when the plunger 51 is in engagement with sleeve 57, the pump work chamber 28 communicates through the bore 37, the annular groove 53 and the axially offset bore 39 with the inside of the pump housing. At rpms below the maximum permissible rpm of the internal combustion engine the piston plunger 51 blocks the bore 39.

The maximum permissible rpm of the internal combustion engine may be set by altering the spring bias 54 at the centrifugal shuttle 38.

What is claimed is:

1. In a fuel injection pump delivering metered fuel to an internal combustion engine and being of the type that has (a) a distributor shaft, (b) a pump work chamber defined within said distributor shaft, (c) piston means operating in said pump work chamber, (d) a rotary component driven by said engine with an rpm that is a function of the engine rpm, (e) a movable control throttle for determining, as a function of its position, the fuel quantities to be injected, (f) rotary electromagnet means coupled to said control throttle to position the same in response to electric signals applied to said rotary electromagnet means, the improvement comprising A. a discharge channel formed as a longitudinal bore in said distributor shaft and connected to said pump work chamber,

B. a movable valve member adapted to assume a first position obturating said discharge channel and a second position opening said discharge channel for depressurizing said pump work chamber and C. centrifugal means mounted to said distributor shaft and including said movable valve member for moving the latter into said second position beyond a predetermined rpm, said distributor shaft being in turn coupled to said rotary component.

2. An improvement as defined in claim ll, said movable valve member being constituted by a piston plunger and said centrifugal means including a centrifugal weight connected to said piston plunger.

3. An improvement as defined in claim 2, including means defining a bore receiving said piston plunger, said rotary component being constituted by a pump shaft, the path of travel of said piston plunger being transversal to the axis of said pump shaft.

4. An improvement as defined in claim 1, including A. an adjustable spring means connected to said movable valve member and opposing its displacement towards said second position and B. abutment means limiting the extent of displacement of said movable valve member. 

1. In a fuel injection pump delivering metered fuel to an internal combustion engine and being of the type that has (a) a distributor shaft, (b) a pump work chamber defined within said distributor shaft, (c) piston means operating in said pump work chamber, (d) a rotary component driven by said engine with an rpm that is a function of the engine rpm, (e) a movable control throttle for determining, as a function of its position, the fuel quantities to be injected, (f) rotary electromagnet means coupled to said control throttle to position the same in response to electric signals applied to said rotary electromagnet means, the improvement comprising A. a discharge channel formed as a longitudinal bore in said distributor shaft and connected to said pump work chamber, B. a movable valve member adapted to assume a first position obturating said discharge channel and a second position opening said discharge channel for depressurizing said pump work chamber and C. centrifugal means mounted to said distributor shaft and including said movable valve member for moving the latter into said second position beyond a predetermined rpm, said distributor shaft being in turn coupled to said rotary component.
 2. An improvement as defined in claim 1, said movable valve member being constituted by a piston plunger and said centrifugal means including a centrifugal weight connected to said piston plunger.
 3. An improvement as defined in claim 2, including means defining a bore receiving said piston plunger, said rotary component being constituted by a pump shaft, the path of travel of said piston plunger being transversal to the axis of said pump shaft.
 4. An improvement as defined in claim 1, including A. an adjustable spring means connected to said movable valve member and opposing its displacement towards said second position and B. abutment means limiting the extent of displacement of said movable valve member. 